It just occurred to me that permutations doesn't quite agree with the mathematical concept:
permutations "aaa" ["aaa","aaa","aaa","aaa","aaa","aaa"]
But that's not really a problem, since you can always just compose
permutations with (Set.toList . Set.fromList).
On Dec 20, 2007 7:05 AM, Twan van Laarhoven
Chris Kuklewicz wrote:
Unfortunately, permutations5 has an error:
I suggest including some QuickCheck properties with this proposal, especially a property that would have caught that error. I'm thinking of four properties: 1) If x = permutations y, then check length x is right. 2) Check each element of x is a permutation of y 3) Check each permutation of y is an element of x 4) Check for laziness By the way, to improve mailing list laziness: the proposal is at http://hackage.haskell.org/trac/ghc/ticket/1990